1. Field of the Invention
This invention relates to a printing press, more particularly to a printing press which obviates the need for interrupting the rotation of a printing roller thereof when adjustments are being made to move the printing roller to a desired position.
2. Description of the Related Art
A printing press has a printing roller on which a printing plate unit is mounted. The printing plate unit rotates synchronously with the printing roller so as to print something onto a printing paper. The printing roller is usually moved to a desired position in order to ensure proper printing of the printing paper. Generally, the printing press includes first, second and third adjusting assemblies. The first adjusting assembly can be actuated to move the printing roller in a direction perpendicular to the longitudinal axis of the printing roller. The second adjusting assembly can be actuated to move the printing roller in a direction parallel to the longitudinal axis of the printing roller. The third adjusting assembly can be actuated to vary an angle formed between the printing plate unit and the longitudinal axis of the printing roller.
Referring to FIG. 1, a conventional printing press 1 is shown to comprise a base support 11. At least one printing assembly 12 is mounted movably on the base support 11. The number of printing assemblies 12 mounted on the base support 11 depends on the number of colors to be printed. Each printing assembly 12 includes two opposite mounting walls 123 and a printing roller 122 which extends horizontally between the mounting walls 123. A printing plate unit (not shown) is mounted on the printing roller 122. In order to correspond the printing plate unit with the printing paper (not shown) to be conveyed into the printing assembly 12, each printing assembly 12 further includes a first adjusting assembly 13, a second adjusting assembly 14 and a third adjusting assembly 15.
Referring to FIGS. 1, 2 and 3, the first adjusting unit 13 includes an actuating rod 132 which extends transversely between two spaced parallel frame portions 111 of the base support 11. One end of the actuating rod 132 extends on one side of the base support 11 and has a hand wheel 131 mounted securely thereon. Two driving gears 133 are mounted securely on the actuating rod 132 and mesh respectively with a driven gear 134. Each of the driven gears 134 is mounted securely on a threaded rod 135. Each of the threaded rods 135 has a mounting seat 136 mounted threadably thereon. The mounting walls 123 are mounted on the mounting seats 136. In operation, rotation of the hand wheel 131 causes corresponding rotation of the actuating rod 132 and the driving gears 133 so as to result in corresponding rotation of the driven gears 134 and the threaded rods 135 in order to move the mounting seats 136 along the respective threaded rods 135, thereby moving the mounting walls 123 relative to the base support 11 in a direction parallel to the mounting walls 123. Movement of the mounting walls 123 results in movement of a longitudinal axis of the printing roller 122 in the direction parallel to the mounting walls 123.
Referring to FIGS. 1 and 4, the second adjusting assembly 14 includes an adjusting rod 142 which extends threadably through a fixed seat 124 mounted on one of the mounting walls 123 and which has a first end portion connected to a bearing 144 on one end of the printing roller 122 and a second end portion extending on one side of the mounting wall 123 opposite to the printing roller 122. A knob 141 is mounted securely on the second end portion of the adjusting rod 142. A stop nut 143 is mounted threadably on the adjusting rod 142 and abuts against the fixed seat 124. In operation, the stop nut 143 is initially moved away from the fixed seat 124. The knob 141 is rotated so as to cause corresponding rotation of the adjusting rod 142. Rotation of the adjusting rod 142 results in longitudinal movement thereof in the direction perpendicular to the mounting walls 123 so as to cause corresponding movement of the printing roller 122. At this time, if the printing plate unit on the printing roller 122 still does not correspond with the printing paper after the actuation of the first and second adjusting assemblies 13,14, actuation of the third adjusting assembly 15 is needed.
Referring to FIGS. 1, 5 and 6, the third adjusting assembly 15 includes four adjusting units 150 which are mounted correspondingly on two inclined surfaces 125 of the printing roller 122. Each of the adjusting units 150 includes a hook member 152 which is retained on the printing roller 122 by means of a press block 151. The press block 151 has a groove within which a base portion of the hook member 152 is received. A hook portion of the hook member 152 extends through a positioning hole 154 of a plate member 153 which is located on the press block 151 and which is coupled to one end of the printing plate unit 16. An adjusting rod 155 extends into the groove and is connected threadably to the base portion of the hook member 152 such that rotation of the adjusting rod 155 results in longitudinal movement of the hook member 152 along the adjusting rod 155. Movement of the hook member 152 causes corresponding movement of the plate member 153, thereby moving the printing plate unit 16 correspondingly. Therefore, rotating the four adjusting rods 155 of the four adjusting units 150 results in movement of the hook members 152, thereby pivoting the printing plate unit 16 relative to the printing roller 122 so as to vary an angle formed between the longitudinal axis of the printing roller 122 and the printing plate unit 16.
From the above disclosure, the position of the printing plate unit 16 relative to the mounting walls 123 must be adjusted by operating the adjusting assemblies 13,14,15 after installation. Since the structures of the adjusting assemblies 13,14,15 are relatively complicated, it is inconvenient to move the printing plate unit 16 to a desired position. For example, four adjusting rods 155 must be rotated simultaneously when varying the angle formed between the longitudinal axis of the printing roller 122 and the printing plate unit 16. In addition, since the four adjusting units 150 are mounted directly on the printing roller 122, the rotation of the printing roller 122 must be interrupted when operating the third adjusting units 15, thereby lowering the adjusting efficiency.